Birefringence is a property of certain materials where the refractive index of the material is dependent upon the polarization and direction of propagation of light through it. I recently learned about it while reading a book on lasers.

Reflection and refraction are phenomena that arise from changes in relative permittivity, and they are exactly the same physical concepts as we see in electromagnetic wave propagation through transmission lines. Fundamentally speaking, they are both aspects of wave impedance, and the calculations used in both arenas are identical.

It therefore occurs to me that birefringence is not limited solely to the domain of optics, and we might also observe the behaviour in electronics - perhaps as some sort of transmission line where the characteristic impedance differs depending on the direction of wave propagation through it.

I suspect that a very tiny amount of birefringence is observable in all conductors, e.g. due to variation in crystalline structure within the metal, but I'm more interested in examples where the magnitude of birefringence is significant enough to be a factor worthy of consideration in practical applications.

Are there any significant examples of birefringence's appearance or exploitation within electronics, specifically in the electrical domain rather than the optical domain?

  • \$\begingroup\$ I am baffled by the "opinion based" close vote on this question. Surely the question of whether or not the physical phenomenon of birefringence is observed in the electrical domain is, by the very definition of the word, objective? \$\endgroup\$
    – Polynomial
    Sep 21 at 12:12
  • \$\begingroup\$ You are asking if there are any significant examples and either the answer is "yes" (which makes your question not very good) or, you are asking for examples in electronics and that is asking for opinions because no single answer is right or wrong. I mean, how would you decide which answer is best? Also, what will happen to this list of examples in a week or a month or a year when some new use is found? In other words, you are asking for opinions and your question is not focussed enough to yield answers that stand the test of time. That's two reasons to vote to close as I see it. \$\endgroup\$
    – Andy aka
    Sep 21 at 12:19
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    \$\begingroup\$ @Andyaka By that second argument one could close almost any question on this site, since new understandings and technologies are always possible, and future developments are a fundamental tenet of the scientific process that should be implicitly assumed. As for whether or not the answer may be a bounded yes (one or two examples given our current understanding and technologies), or an unbounded yes (it's everywhere), or a no - I could not possibly know which it is before receiving an answer, so to argue that this question should be closed because one of those might be the case is a tautology. \$\endgroup\$
    – Polynomial
    Sep 21 at 12:35
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    \$\begingroup\$ Basically all flexible waveguides are anisotropic if you bend them, so it appears as a nuisance in cabling. I'm not sure of productive uses. In optics, material birefringence is widely used in free space optics (splitters, attenuators, isolators), whereas free space electronic components are not so common due to the longer wavelengths. \$\endgroup\$ Sep 21 at 13:07
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    \$\begingroup\$ Unwanted anisotropy shows up in lots of places, especially at high frequencies. PCBs are made of fiberglass and so have birefringence between the fiber axis and perpendicular axes. Bending any waveguide does something similar. For very high frequency interconnects (PCIe 5, USB4, DDR5, etc), a lot of effort goes into manufacturing devices (PCBs, coaxial cables, etc) that have relatively uniform, isotropic properties. \$\endgroup\$ Sep 21 at 14:04


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